In the oil and gas industry, subterranean formations penetrated by a wellbore are often hydraulically fractured to enhance hydrocarbon production. Hydraulic fracturing operations are typically carried out by strategically isolating various zones of interest (or intervals within a zone of interest) in the wellbore using packers and the like, and then subjecting the isolated zones to a variety of treatment fluids at increased pressures.
Today, it is possible to stimulate multiple zones during a single stimulation operation by using onsite stimulation fluid pumping equipment. In such applications, several packers are introduced into the wellbore and each packer is strategically deployed at predetermined intervals that isolate adjacent zones of interest. Each zone may have a sliding sleeve movably disposed within a casing that lines the wellbore. Each sliding sleeve may be movable between a closed position, where the sliding sleeve occludes one or more flow ports defined in the casing at that location, and an open position, where the flow ports are exposed and fluid communication is allowed between the casing and the surrounding formation.
The sliding sleeves may be selectively shifted to the open position using, for instance, a ball drop system, which sequentially drops wellbore projectiles from a surface location into the wellbore. The wellbore projectiles, commonly referred to as “frac balls,” are of predetermined sizes configured to seal against correspondingly sized baffles or seats associated with each sliding sleeve. Smaller frac balls are introduced into the wellbore prior to the larger frac balls, where the smallest frac ball is designed to land on the baffle furthest from the wellhead, and the largest frac ball is designed to land on the baffle closest to the wellhead. Applying hydraulic pressure from the surface serves to shift the target sliding sleeve to its open position.
Some wellbores have extended horizontal portions and a tight surrounding subterranean formation can make it difficult to achieve the necessary flow rates to carry wellbore projectiles to target baffles to actuate the sliding sleeve.